Various types of insulating materials are widely used to prevent or reduce heat transfer between separated spaces. Many of the insulating materials used need not be high strength materials since they bear little or no compressive loads. However, some of the insulating materials are used as foundation or base materials and as a result they must be able to withstand compressive loads of 50 to 100 psi or greater. In addition to bearing the applied load, the insulating material must often be able to withstand wide temperature cycles, such as from ambient temperature to -200.degree. F. or lower, without loss of, or change in, physical properties. This is especially so if the insulation is used in a cryogenic storage tank.
Many of the load bearing insulating materials are lightweight because they have a cellular structure, which enhances their insulating property, i.e., gives a lower thermal conductivity or K value. The cellular structure, however, often leads to a reduction in compressive strength. Insulating materials with a cellular structure having good compressive strength and good insulating properties are accordingly in demand. One type of such material which has such properties and maintains them in cryogenic use is foamed glass, one such product being commercially available as FOAMGLAS. Foamed glass is relatively expensive so a less expensive, though equally or better suited, product is desired.
It has been previously proposed to use foamed concretes as insulating materials. However, they have had one or more shortcomings, such as insufficient strength or poor insulating values, which have made them unsuitable for many uses, particularly in cryogenic storage structures. A need accordingly exists for a suitable lightweight insulating concrete having relatively high compressive strength with good low temperature of cryogenic insulating properties and which is made of low or reasonably priced ingredients.